Geology of the terrestrial planets 2014 Pearson Education, Inc.
Earth s Bulk Properties
Earth s Bulk Properties albedo - A = 0.39 A = 0 planet absorbs all sunlight that hits it A =1 planet reflects all sunlight that hits it Surface temperature - T = 9 C = 48 F = 282 K Ave Surface temperature - T = 60 C =140 F = 333 K max Surface temperature - T = 90 C = 130 F =183 K min
Moon s Bulk Properties Diameter D = 3476 km = 1 4 D Rotation period = orbital period 1 month Average density = 3344 kg/m 3 Escape speed = 2400 m/s = 5400 mph Avg daytime temperature = 130 C = 266 F Avg nighttime temperature = 180 C= 292 F
Mercury s Bulk Properties Notice that Mercury s rotation period is 2/3 of its orbital period.
Mercury s Bulk Properties Average density = 5430 kg/m 3 = 0.98 density of Earth Escape speed - v escape = 4.3 km/s = 9,700 mi/h Average daytime temperature = 350 C = 662 F = 623 K Average nighttime temperature = 170 C = 274 F =103 K The low escape speed and high temperature of Mercury prevent it from retaining an atmosphere Without an atmosphere, the planet s surface temperature cannot be regulated effectively
Venus Bulk Properties Mass - M = 4.87 10 24 kg = 0.815M Earth Diameter - D Earth =12,104 km = 0.949D Earth Orbital eccentricity - e = 0.0068 Orbital period (sidereal) - P = 224.7 d Rotation period = 243.0 d Based upon the first 2 properties, Venus is sometimes referred to as Earth s twin Almost perfectly circular orbit Sidereal day on Venus is longer than its sidereal year
Venus Bulk Properties The temperature on Venus is fairly constant over the entire planet. Why might that be the case? Thick, dense atmosphere At its brightest Venus is the 3 rd brightest object in the sky high albedo fairly close proximity to Earth & Sun
Mars Bulk Properties Some similarities between Mars & Earth Mars has days & seasons like Earth
Mars Bulk Properties Many differences between Mars & Earth Mars has density similar to Moon Even though atmosphere of Mars is mostly CO 2 there isn t enough atmosphere for greenhouse effect to keep Mars warm
Terrestrial Planet Interiors 2014 Pearson Education, Inc.
Earth's Interior Core: highest density; nickel and iron Mantle: moderate density; silicon, oxygen, etc. Crust: lowest density; granite, basalt, etc. 2014 Pearson Education, Inc.
Chemical Differentiation Process by which denser material sinks and less dense material floats Effectively separates different chemical species
Crust Relatively low density, rocky surface layer we live on Mostly composed of silicon-rich rocks Very thin layer <40 km thick Earth s radius is 6400 km Average density 3500 kg/m 3
Lithosphere A planet's outer layer of cool, rigid rock is called the lithosphere. It "floats" on the warmer, softer rock that lies beneath. 2014 Pearson Education, Inc.
Mantle Fairly thick middle layer Composed of iron-rich rock Extends from crust down 2900 km Average density 3500-5500 kg/m 3
Central region of Earth Composed of almost pure iron Outer core liquid iron layer 2900-5100 km depth Average density 10,000-12,000 kg/m 3 Inner core solid iron crystal 5100-6400 km depth Average density 13,000 kg/m 3 Core
Thought Question What is necessary for differentiation to occur in a planet? a) It must have metal and rock in it. b) It must be a mix of materials of different density. c) Material inside must be able to flow. d) All of the above e) b and c 2014 Pearson Education, Inc.
Thought Question What is necessary for differentiation to occur in a planet? a) It must have metal and rock in it. b) It must be a mix of materials of different density. c) Material inside must be able to flow. d) All of the above e) b and c 2014 Pearson Education, Inc.
Heating of Planetary Interiors Accretion and differentiation when planets were young Radioactive decay is most important heat source today. 2014 Pearson Education, Inc.
Cooling of Planetary Interiors Convection transports heat as hot material rises and cool material falls. Conduction transfers heat from hot material to cool material. Radiation sends energy into space. 2014 Pearson Education, Inc.
Role of Size Smaller worlds cool off faster and harden earlier. The Moon and Mercury are now geologically "dead." 2014 Pearson Education, Inc.
Refraction of Seismic Waves Refraction refers to the bending of waves Seismic waves refract (or bend) when they pass from material of one density to material of another density
What processes shape planetary surfaces? 2014 Pearson Education, Inc.
Processes That Shape Surfaces Impact cratering Impacts by asteroids or comets Volcanism Eruption of molten rock onto surface Tectonics Disruption of a planet's surface by internal stresses Erosion Surface changes made by wind, water, or ice 2014 Pearson Education, Inc.
Impact Cratering Most cratering happened soon after the solar system formed. Craters are about 10 times wider than object that made them. Small craters greatly outnumber large ones. 2014 Pearson Education, Inc.
Impact Craters Meteor Crater (Arizona) Tycho Crater (Moon) 2014 Pearson Education, Inc.
Impact Craters on Mars "Standard" crater Impact into icy ground Eroded crater 2014 Pearson Education, Inc.
Volcanism Volcanism happens when molten rock (magma) finds a path through lithosphere to the surface. Molten rock is called lava after it reaches the surface. 2014 Pearson Education, Inc.
Lava and Volcanoes Runny lava makes flat lava plains. Slightly thicker lava makes broad shield volcanoes. Thickest lava makes steep stratovolcanoes. 2014 Pearson Education, Inc.
Outgassing Volcanism also releases gases from Earth's interior into the atmosphere. 2014 Pearson Education, Inc.
Tectonics Convection of the mantle creates stresses in the crust called tectonic forces. Compression of crust creates mountain ranges. Valley can form where crust is pulled apart. 2014 Pearson Education, Inc.
Plate Tectonics Earth s crust is not one solid piece of rock Instead it is a jigsaw puzzle of plates
Plate Tectonics Plate motions create rifts and mountain ranges rifts
Plate Tectonics Plates are moving relative to one another
Plate Tectonics Plates are moving relative to one another
Plate Tectonics Plates are moving relative to one another
Formation of Lunar Maria Early surface is covered with craters. Large impact crater weakens crust. Heat buildup allows lava to well up to surface. Cooled lava is smoother and darker than surroundings. 2014 Pearson Education, Inc.
Tectonic Features Wrinkles arise from cooling and the contraction of a lava flood. 2014 Pearson Education, Inc.
Geologically Dead Moon is considered geologically "dead" because geological processes have virtually stopped. 2014 Pearson Education, Inc.
Surface of Mercury Oldest Youngest Mercury Lunar highlands Lunar Mare 4 billion yrs 3 billion yrs
Tectonics on Mercury Long cliffs indicate that Mercury shrank early in its history. 2014 Pearson Education, Inc.
Venus
Radar Mapping Insert TCP7e figure 9.35 Its thick atmosphere forces us to explore Venus's surface through radar mapping. 2014 Pearson Education, Inc.
Cratering on Venus Venus has impact craters, but fewer than the Moon, Mercury, or Mars. 2014 Pearson Education, Inc.
Volcanoes on Venus It has many volcanoes, including both shield volcanoes and stratovolcanoes. 2014 Pearson Education, Inc.
Tectonics on Venus The planet's fractured and contorted surface indicates tectonic stresses. 2014 Pearson Education, Inc.
Erosion on Venus Photos of rocks taken by landers show little erosion. 2014 Pearson Education, Inc.
Surface of Venus Venus has a relatively young surface approximately 500 million years old Earth s surface is about 200 million years old on average Mercury s surface is more than 3 billion years old Venus has about 1000 large craters on surface more than Earth, but far fewer than Mercury or the Moon
Surface of Venus Why is the surface of Venus so young? Perhaps we should start with the question, why is the Earth s surface so young? For Earth, the young surface is the result of plate tectonics The crust of Venus appears to be made of a single piece of rock No plates that can shift with respect to one another Entire surface of Venus appears to be roughly the same age Unlike the Earth or the Moon, which have regions of much different ages Evidenced by the uniform distribution of craters over the surface of Venus
Surface of Venus Hypotheses to explain young surface equilibrium resurfacing hypothesis widespread volcanism across all of Venus surface renews rock at a relatively constant rate craters are covered by new rock at about the same rate that the craters form global catastrophe hypothesis an intense period of eruptions 500 million years ago rapidly resurfaced all of Venus
Intelligent Life on Mars? In science fiction, Mars has been one of the most frequent sites for extra-terrestrial life forms This has some basis in scientific discoveries that have been misinterpreted Face on Mars Canals on Mars Viking 1, 1976 Exploring Mars, 1894
Intelligent Life on Mars? In science fiction, Mars is one of the most frequent sites for extra-terrestrial life forms This has some basis in scientific discoveries that have been misinterpreted Face on Mars Canals on Mars Mars Global Surveyor, 2001 Hubble Space Telescope, 2003
Water on Mars? No liquid water on Mars surface now Evidence water has flowed on surface of Mars in the past ancient riverbeds
Water on Mars? Evidence water has flowed on surface of Mars in the past ancient floods 1000 times the flow rate of Mississippi R.
Water on Mars? Evidence water has flowed on surface of Mars in the past canyons carved by flowing water
Erosion of Craters Details of some craters suggest they were once filled with water. Insert TCP7e Figure 9.29 2014 Pearson Education, Inc.
Martian Rocks Mars rovers have found rocks that appear to have formed in water. 2014 Pearson Education, Inc.
Ice on Mars Although there is still no certain evidence that liquid water flowed on Mars surface, there is evidence of ice on Mars polar ice caps dry ice (CO 2 ) water ice
Subsurface ice Permafrost
Permafrost Subsurface ice Melted by meteor strikes Create mud flows around crater
Topography of Mars Mars appears to be divided into 2 very different parts Divided almost exactly along the equator
Topography of Mars Northern lowlands northern hemisphere is nearly 5 km (3 mi) lower than southern hemisphere Southern highlands
Topography of Mars Fewer craters in northern hemisphere Northern lowlands are younger
Crustal Dichotomy Hypotheses Massive impact from meteorite or asteroid similar to lunar maria Plate tectonic activity in Martian past northern lowlands are new rock from crustal spreading similar to Earth s Atlantic Ocean Ancient ocean covered northern lowlands young rocks are sedimentary rocks from bottom of ocean
Volcanism on Mars Mars has many large shield volcanoes. Olympus Mons is largest volcano in solar system. 15 mi. high 2014 Pearson Education, Inc.
Geologic Features Valles Marineris would stretch from Los Angeles to New York 2500 mi long, 400 mi wide, 5 mi deep
Iron on Mars Reddish color on surface of Mars due to iron oxide (rust) However, low density suggests no dense iron core Conclusions? Mars did not undergo large-scale chemical differentiation Must have a lower percentage of iron relative to other elements compared to other terrestrial planets
Terrestrial Planet Interiors 2014 Pearson Education, Inc.
Role of Planetary Size Smaller worlds cool off faster and harden earlier. Larger worlds remain warm inside, promoting volcanism and tectonics. Larger worlds also have more erosion because their gravity retains an atmosphere. 2014 Pearson Education, Inc.
Role of Distance from Sun Planets close to the Sun are too hot for rain, snow, ice and so have less erosion. Hot planets have more difficulty retaining an atmosphere. Planets far from the Sun are too cold for rain, limiting erosion. Planets with liquid water have the most erosion. 2014 Pearson Education, Inc.
Role of Rotation Planets with slower rotation have less weather, less erosion, and a weak magnetic field. Planets with faster rotation have more weather, more erosion, and a stronger magnetic field. 2014 Pearson Education, Inc.
Thought Question How does the cooling of planets and potatoes vary with size? a) Larger size makes it harder for heat from inside to escape. b) Larger size means a bigger ratio of volume to surface area. c) Larger size takes longer to cool. d) all of the above 2014 Pearson Education, Inc.
Thought Question How does the cooling of planets and potatoes vary with size? a) Larger size makes it harder for heat from inside to escape. b) Larger size means a bigger ratio of volume to surface area. c) Larger size takes longer to cool. d) all of the above 2014 Pearson Education, Inc.
Sources of Magnetic Fields Motions of charged particles are what create magnetic fields. 2014 Pearson Education, Inc.
Sources of Magnetic Fields A world can have a magnetic field if charged particles are moving inside. Three requirements: Molten, electrically conducting interior Convection Moderately rapid rotation 2014 Pearson Education, Inc.
Earth s Magnetic Field Earth s magnetic pole does not line up exactly with Earth s geographic pole (rotation axis) Magnetic pole is tilted 11.5 from the rotation axis Earth s geographic north pole is really the magnetic south pole
Earth s Magnetic Field Magnetic north pole is currently located near Ellef Ringnes Island in northern Canada Location of magnetic north pole changes with time Year Latitude ( N) Longitude ( W) 2001 81.3 110.8 2002 81.6 111.6 2003 82.0 112.4 2004 82.3 113.4 2005 82.7 114.4
Role of Earth s Magnetic Field Protects the Earth from cosmic radiation, particularly the charged particles in the solar wind Region over which the Earth s magnetic field dominates is called the magnetosphere Most of the charged particles in the solar wind and cosmic radiation get deflected by magnetic field Some get captured in the Van Allen belts
Van Allen Belts 2 doughnut shaped rings around the Earth Inner belt contains mostly heavier particles (protons) Outer belt contains lighter particles (electrons)
Auroras
Auroras
Auroras
Mercury s Magnetosphere
Mercury as Seen From Earth Despite occasionally being bright enough to see with the naked eye, Mercury is so small that it is virtually impossible to see any details with Earth-based telescopes
Mercury has Phases 1 st Quarter and waxing gibbous Mercury Why is the waxing gibbous image smaller than the 1 st Quarter?
Planet passes across the face of the Sun as observed from Earth What planets can exhibit solar transits? Why might it be useful to carefully observe solar transits? Solar Transit
Exploration of Mercury Mercury is the only terrestrial planet on which no human spacecraft have landed First scientific mission to Mercury was Mariner 10 1974-1975
Exploration of Mercury MESSENGER MErcury Surface, Space ENvironment, GEochemistry, & Ranging http://messenger.jhuapl.edu/
Visiting Venus If you were to land on Venus, you would: boil almost instantly from the extreme heat suffocate from the lack of oxygen be crushed by the overwhelming pressure of the atmosphere be burned by sulfuric acid droplets in the air Note: These are in no particular order
Visiting Venus Soviet Venera spacecraft did visit the surface of Venus None lasted more than a few hours